This invention relates to strippers which strip a web material from a conveyor surface in a web handling device. More particularly, the invention relates to a novel arrangement of stripper fingers and a shut down mechanism to produce a jam prevention means whereby damage to the web handling device is eliminated or minimized. The novel combination operates to sense a blockage occurring in the web handling device and shut the device down before any serious damage is done.
The web handling device can be any type of machine which moves a web at high speed, including such devices as xerographic or electrostatic printing machines, cloth handling machines for printing and dying fabrics, high-speed printing presses, or feeders and folding apparatus associated with such web handling devices. The invention is most preferably used with a high-speed printing press.
The web may be any cellulosic, plastic, or other material which can be formed into a sheet, ribbon, or roll, such as natural or man-made fabrics, thin plastic films, or paper. The web may be either in the form of a continuous ribbon, discontinuous sheets, or combinations of either of these such as bandage rolls, signatures consisting of a number of folder sheets or a bundle of sheets.
Web handling devices perform a number of operations which require a web to be stripped from a conveyor surface such as a plate or drum by stripper fingers. The fingers help to remove the web from one surface and guide it to the next station in the web handling device.
The stripper fingers used to strip a web may be of the stationary type or the moving type. Stationary stripper fingers are passive and accomplish the stripping operation by deflecting the web in a desired direction. They may operate in any one of a number of locations, including grooves in the conveyor surface, level with the conveyor surface, or raised less than a web thickness above the conveyor surface. Stationary type stripper fingers are illustrated in U.S. Pat. No. 3,992,000 to Martin or U.S. Pat. No. 4,156,524 to Ari bar-On. In contrast, the moving stripper fingers use a controlled or timed movement to flip the web from one conveyor surface to another. Moving type stripper fingers are illustrated in U.S. Pat. No. 3,450,402 to Weiler, U.S. Pat. No. 3,578,859 to Stillings, or U.S. Pat. No. 4,004,802 to Brooke.
Occasionally, the web fails to be properly guided from the conveyor surface by the stripper fingers and a blockage is created which causes the web to jam. This jam can be destructive to the web handling device as well as causing a loss of operating time. This is particularly true in large high-speed presses where jams can develop in the associated folding apparatus such as that described in U.S. Pat. No. 966,095 to Hollingsworth, U.S. Pat. No. 1,784,757 to Scott, or U.S. Pat. No. 3,717,337 to McCain et al. Since the high-speed press and any associated equipment is operating at very high speeds, any jam in the web flow will cause a large volume of such material to be jammed into a small area before an operator can manually shut down the press. Such a jam not only causes a loss of valuable web material but also requires considerable time and effort to undo. Such a jam can commonly be so tight that crow bars and extensive equipment disassembly are required to undo the jam. Such a disassembly operation causes a loss of time and delays completion of the job. Very often the stripper fingers, guides, and other parts of the press are broken or bent by the jam causing increased expenses for parts.
In some office xerographic copying machines, the paper flow is controlled by complex electric eyes or optical devices counting the passing sheets or pressure switches which are struck by an out of place sheet. These mechanism are impractical for high-speed, heavy duty devices which process the web in the form of a fabric, a signature, a bundle of sheets, or the like. For these devices stripper fingers are preferred because they have the ruggedness and longevity necessary for satisfactory and economical operation of the device.
Therefore, it is the object of this invention to provide a novel arrangement of stripper fingers and a shut down mechanism which will prevent jams. It is another object of this invention to provide a means to shut down the web handling device when blockage of the web occurs so as to eliminate or minimize damage to the web handling device. Further, it is an object of this invention to provide a means to reduce or eliminate damage to stripper fingers, conveyors, or the like in web handling devices. In addition, it is an object of this invention to provide a means to reduce or eliminate lost time resulting from jams at the stripper fingers in web handling devices. Other objects and advantages of the invention will become apparent upon reading the description of the preferred embodiments with reference to the drawings.